The Roman Army was one of the most disciplined and efficient armies the world has ever seen. It allowed Rome to conquer and most importantly effectively garrison and police regions as far apart and diverse as Britannia (modern day England) in the North, Aegyptus (modern day Egypt) in the South, Lusitania (modern day Portugal) in the West and Palmyra (Eastern Syria) in the East. The reason for this was that the Roman army structure was flexible and yet well defined, in short, it was a ruthlessly professional army, the likes of which the world would not see again until the Age of Industrialism.
The Roman Army was organised in such a manner that it could operate equally effectively in the marshes of Britannia and the blistering North African desert. This article aims to provide a concise view into the Roman army structure and legionary ranks after the Marian reforms.
Roman Army Structure
The structure of the Roman army still forms the structure of modern armies due to its flexibility and clearly defined chain of command. Although it is different in certain key ways, anyone who knows the basic organisation of a modern army will be able to spot many similarities.
The basic organisational and tactical unit of the army was the Century comprising of 80 men. These were divided into 9 Contubernia of 8 men each which shared a tent (during campaigns) or barracks (when garrisoned) and shared one mule to carry heavy equipment. A Century was led by a Centurion who was assisted by an Optio (second in command), a Tesserarius (guard commander), an Actarius (clerk) and a Signifer (standard bearer) besides other ranks.
Six Centuries were organised into a Cohort, thus containing around 480 men. Centurions were appointed to the Centuria on the basis of seniority, with the most senior Centurion having direct command of the First Century and overall command of the Cohort. In order of ascending seniority, the Centurions of a cohort were called Hastatus Posterior, Hastatus Prior, Princeps Posterior, Princeps Prior, Pilus Posterior and Pilus Prior. Thus the commander of the Cohort would be the Pilus Prior. The Pilus Posterior would take over if the Pilus Prior died, was wounded, had gone missing missing or was absent from combat.
The largest administrative unit of the Roman army was the Legion. Each legion had 10 cohorts with around 5240 men. The first cohort had 5 centuries of 160 men each (double size) which totalled 800 men, there was also a complement of 120 auxiliary or legionary cavalry, however they were used for scouting and sending messages rather than in combat.
The legion may also have auxiliary cohorts attached depending on the type of operation it was undertaking, enemy tactics, and a myriad other reasons. Including Architecti (engineers), Immunes (soldiers with specialist duties which were excused from drill, fatigues, etc, however each was a fully trained Legionary and could be called upon to fight), Speculatores and Exploratores (scouting elements), Medicus (various types of medics), a fully manned Legion would probably number around 5700 men.
Each legion was commanded by the Legatus Legionis who was usually appointed for 2-3 years though there were many exceptions. Officially the Tribunus Laticlavius was the second in command, however in reality the Praefactus Castorum (camp prefect) would take over. Efficient and professional Legates would welcome advice from the vastly more experienced Praefactus Castorum in military matters. The legate also had at his disposal 6 Tribunes Militum (from the Senatorial class), one of whom was the Tribunus Laticlavius (wore a broad striped toga and was destined for a career in the military) and the remaining 5 were Tribunes Angusticlavii (wore narrow striped toga and were only serving for a short time to gain experience in the military).
During campaigns and in certain provinces (depending on size or unrest), two or more legions were sometimes stationed together. These were commanded by a Legatus Augusti Pro Praetorae (Imperial Legate) who was appointed for 2-3 years. He also served as the governor of the province in which he was stationed.
Roman Army Ranks
Roman society was divided on the basis of class, this was reflected in the Roman army. There were basically 4 social classes in ancient Rome; the Plebians, the Equestrians and the Patricians, these 3 classes were comprised of Roman citizens and the fourth class was that of the non-citizens, the slaves and the freedmen. This division was mainly on the basis of wealth, thus a Plebian could become an Equestrian by amassing enough wealth.
The Plebians could join the army as Legionaries and could be promoted to Optio and the various Centurion ranks; the Praefactus Castorum who was promoted from the Centurionate too was a Plebian. Some Centurions were promoted to Tribunes Militum during Augustus’s reign due to outstanding performance; once promoted, they would attain the Equestrian class of society, however this was extremely rare.
The Equestrians were given command of the auxiliary cohorts and could be appointed as Tribunes Militum by imperial decree.
The Patricians or Senators were given the most powerful positions in the army, the Roman army ranks of Legatus Legionis, Legatus Augusti Pro Praetorae, Tribunus Militum (exceptions mentioned above) were all filled exclusively by the Patricians.
The non-citizens could join up as auxiliaries and provide specialist skills to the Roman army. Auxiliaries were paid half as much as Legionaries and were granted Roman citizenship at the end of 25 year’s service. Slaves could not serve in the army, however the children of freemen were given citizenship and could serve as Legionaries.
Although social status put certain restrictions on an individual in the Roman army, it is important to note that the entire Centurionate, which provided the discipline and training in the army was comprised of Plebians; the third in command (the Praefactus Castorum) of a Legion was a Plebian and ranked over 5 Patricians (unofficially 6); Plebians could rise to Equestrian rank. Analysis of the medical service shows that most surgeons were from the Eastern half of the Empire, mostly Greece, North Africa and the Levant, further proof that the Romans were not concerned with social status or background, only with skill and aptitude. However the greatest example that proves inconclusively that the Roman army was professional to the very core is the very existence auxiliary branch of the army, which provided almost all specialist skills of the army like missile support (excluding artillery) and cavalry.
It would be safe to conclude that the Roman army was very forward thinking for its time (post decline of the Roman Empire, social status still played a role in military leadership until the 1600’s). In short, the Roman army structure valued skill and ability rather than social status which showed its professionalism.
A very warm thanks to all the readers. This is my first article in this blog and so I’m sorry for any mistakes that I may have made in writing this. Please comment below with any questions or advice you have and I will try my best to reply to them. My subsequent articles will elaborate a bit on the Roman army structure but mainly focus on the Roman army and its abilities and tactics, if you would like me to cover any other areas of history, please let me know in the comments. Thanks for your time.